While the parent applications relate mainly to the field of anti-counterfeiting and authentication methods and devices, the present invention aims mainly at synthesizing band moiré images (called “moiré patterns” in patent application Ser. No. 10/270,546) and shape level lines (patent application Ser. No. 11/149,017) for making the information forwarded by time pieces such as watches and clocks, and by valuable articles (cosmetics, perfumes, drugs, jewelry, bikes, cars, publicity display devices, postcards and fashionable clothes) more dynamic, as well as for improving their attractiveness and aesthetics. As described in the parent patent applications, the synthesized band moiré and shape level line images also provide a strong protection against counterfeiting attempts.
Publicity can also benefit from the visually striking message forwarded by dynamically evolving superposition images resulting from the superposition of a base layer and a revealing layer, with one of the layers being in movement in respect to the other layer.
The theory on which the present invention relies has been partly published at the beginning of August 2004, as a scientific contribution: “Band Moiré Images”, by R. D. Hersch and S. Chosson, SIGGRAPH'2004, ACM Computer Graphics Proceedings, Vol. 23, No. 3. pp. 239-248.
Moiré and phase effects have been used in the prior art for the authentication of documents. For example, thanks to the phase modulation effect, it is possible to make visible a hidden pattern image encoded within a document (see background of U.S. Pat. No. 5,396,559 to McGrew, background of U.S. Pat. No. 5,901,484 to Seder, U.S. Pat. No. 5,708,717 to Alasia and U.S. Pat. No. 5,999,280 to Huang). When a line grating or a grating of lenticular lenses is superposed on such a document, the pre-designed latent image becomes clearly visible. This phase effect has the particularity that the latent image does not move. When moving the revealing layer on top of the base layer, the latent image foreground becomes alternatively dark and highlight. A further variation of the phase shift technique using conjugate halftone screens is described in U.S. Pat. No. 5,790,703 to Shen-ge Wang. Additional variations of the phase sampling techniques comprising screen element density, form, angle position, size and frequency variations are described in U.S. Pat. No. 6,104,812 to Koltai et. al. A further variation of the phase shift technique consists in having similar line segments printed in registration on two sides of a thick transparent layer: thanks to the parallax effect, the superposition of both layers can be viewed either in phase or out of phase depending on the observation angle, see U.S. Pat. No. 6,494,491 B1 to P. Zeiter et al.
The disclosed band moiré image synthesizing methods (parent U.S. patent application Ser. Nos. 10/270,546, 10/879,218 and 11/349,992) completely differ from the above mentioned phase shift techniques since no latent image is present when generating a band moiré image and since the band moiré image shapes resulting from the superposition of a base band grating and a revealing line grating are a geometric transformation of the original shapes embedded within each band of the base band grating. This geometric transformation comprises always an enlargement, and possibly a rotation, a shearing, a mirroring, and/or a bending transformation. In addition, in the present invention, specific base band grating and revealing line grating layers can be created which upon translation, respectively rotation of the revealing layer in superposition with the base layer, yield a displacement of the band moiré image shapes. Phase based modulation techniques allowing to hide latent images within a base layer are not capable of smoothly displacing and possibly transforming the revealed latent image when moving the revealing layer on top of the base layer.
In U.S. Pat. No. 5,712,731 (Drinkwater et al.) a moiré based method is disclosed which relies on a periodic 2D array of microlenses. This last disclosure has the disadvantage of being limited to the case where the superposed revealing structure is a microlens array and the periodic structure on the document is a constant 2D array of identical dot-shapes replicated horizontally and vertically. Thus, in contrast to the present invention, that invention excludes the use of gratings of lines as the revealing layer. A similar 2D array of microlenses is disclosed in patent application Ser. No. 10/995,859 to Steenblik et. al., filed Nov. 22, 2004. Both inventions also consider a fixed setup of microlens array and dot shape array separated by a gap, where changing the observation orientation has the effect of moving and changing the size of the resulting 2D moiré patterns.
Other moiré based methods disclosed by Amidror and Hersch in U.S. Pat. No. 6,249,588, its continuation-in-part U.S. Pat. No. 5,995,638 and U.S. Pat. No. 6,819,775, rely on the superposition of arrays of screen dots, possibly geometrically transformed, which yields a moiré intensity profile indicating the authenticity of the document. These inventions are based on specially designed 2D structures, such as dot-screens (including variable intensity dot-screens such as those used in real, gray level or color halftoned images), pinhole-screens, or microlens arrays, which generate in their superposition periodic moiré intensity profiles of chosen colors and shapes (typographic characters, digits, the country emblem, etc.) whose size, location and orientation gradually vary as the superposed layers are rotated or shifted on top of each other. These methods making use of the moiré intensity profile to authenticate documents have two limitations. The first limitation is due to the fact that the revealing layer is made of dot screens, i.e. of a set (2D array) of tiny dots laid out on a 2D surface. When dot screens are embodied by an opaque layer with tiny transparent dots or holes (e.g. a film with small transparent dots), only a limited amount of light is able to traverse the dot screen and the resulting moiré intensity profile is not easily visible. The second limitation is due to the fact that the base layer is made of a two-dimensional array of similar dots (dot screen) where each dot has a very limited space within which only a few tiny shapes such as a few typographic characters or a single logo can be placed.
In parent U.S. patent application Ser. No. 10/270,546 (filed 16 Oct. 2002, “Authentication of documents and articles by moiré patterns”, inventors Hersch and Chosson), a significant improvement was made by the discovery that a rectilinear base band grating incorporating original shapes superposed with a revealing straight line grating yields rectilinear moiré bands comprising moiré shapes which are a linear transformation of the original shapes incorporated within the base band grating. These moiré bands form a band moiré image. Since band moiré images have a much better light efficiency than moiré intensity profiles relying on dots screens, band moiré images can be advantageously used in all case where the previous disclosures relying on 2D screens fail to show strong enough moiré shapes. In particular, the base band grating incorporating the original shapes may be printed on a reflective support and the revealing line screen may simply be a film with thin transparent lines. Due to the high light efficiency of the revealing line screen, the band moiré shapes representing the transformed original base band shapes are clearly revealed. A further advantage of band moiré images resides in the fact that it may comprise a large number of shapes, for example one or several words, one or several sophisticated logos, one or several symbols, and one or several signs.
U.S. patent application Ser. No. 10/270,546 (inventors: Hersch and Chosson), describes the layout of rectilinear band moiré images, when the layouts of base layer and the revealing layer are known. However it does not tell in which direction and at which speed the moiré shape moves when translating the rectilinear revealing layer in superposition with the rectilinear base layer. Furthermore, since it does not disclose a model for predicting the layout of the moiré image that can be produced when superposing a curvilinear base layer and a curvilinear revealing layer, band moirés image relying on curvilinear base or revealing layers need to be generated by a trial and error procedure. Furthermore, U.S. patent application Ser. No. 10/270,546 (Hersch and Chosson) does neither give a precise technique for generating a reference rectilinear band moiré image layout with curvilinear base and revealing layer layouts nor does it give a means of generating a desired reference curvilinear band moiré image layout with a predetermined rectilinear or curvilinear revealing layer layout.
The band moiré synthesizing method, drawn from parent U.S. patent application Ser. No. 10/879,218 (inventors: Hersch and Chosson), relies on a band moiré image layout model allowing to compute not only the layout of a rectilinear band moiré image produced by superposing a rectilinear base band layer and a rectilinear revealing layer, but also in which direction and at which speed the rectilinear moiré shapes move when translating a the rectilinear revealing layer in superposition with the rectilinear base layer. For a curvilinear base layer and a curvilinear or rectilinear revealing layer, that model computes exactly the layout of the resulting rectilinear or curvilinear band moiré image obtained by superposing the base and revealing layers. Furthermore, one may specify a desired rectilinear or curvilinear band moiré image, as well as one of the layers and the model is able to compute the layout of the other layer. In addition, one may specify the direction in which band moiré image moves when translating or rotating the revealing layer.
In the prior art, the properties of the moiré produced by the superposition of two line gratings are well known (see for example K. Patorski, The moiré Fringe Technique, Elsevier 1993, pp. 14-16). Moiré fringes (moiré lines) produced by the superposition of two line gratings (i.e. set of lines) are exploited for example for the authentication of banknotes as disclosed in U.S. Pat. No. 6,273,473, Self-verifying security documents, inventors Taylor et al. Curved moiré fringes (moiré lines) produced by the superposition of curvilinear gratings are also known (see for example Oster G, Wasserman M., Zwerling C. Theoretical Interpretation of Moiré Patterns. Journal of the Optical Society of America, Vol. 54, No. 2, 1964, 169-175) and have been exploited for the protection of documents by a holographic security device (U.S. Pat. No. 5,694,229, issued Dec. 2, 1997, K. J. Drinkwater, B. W. Holmes).
In parent U.S. patent application Ser. Nos. 10/270,546, 10/879,218, and 11/349,992, as well as in the present application, instead of using a line grating as base layer, we use as base layer a band grating incorporating in each band an image made of one-dimensionally compressed original patterns of varying shapes, sizes, intensities and possibly colors. Instead of obtaining simple moiré fringes (moiré lines) when superposing the base layer and the revealing line grating, we obtain a band moiré image which is an enlarged and transformed instance of the original base band image.
Joe Huck, a prepress professional, in his publication (2003) entitled “Mastering Moirés. Investigating Some of the Fascinating Properties of Interference Patterns, see also http://pages.sbc-global.net/joehuck”, created band moiré images, both for artistic purposes and for creating designs incorporating moiré shapes floating within different perceived depth planes thanks to parallax effects. His publication only reports about vertically replicated horizontal base bands and a revealing layer made of horizontal lines, thereby generating moiré shapes moving only in the vertical direction. In contrast to the present invention, he did not provide a general-purpose framework for predicting the geometry of band moiré images as a function of base and revealing layer layouts, nor did he consider geometric transformations of base and revealing layers. In addition, he didn't consider using band moiré images for displaying information on watches and valuable articles by creating a displacement between base and revealing layer.
The described elevation profile embedding method, drawn from parent U.S. patent application Ser. No. 11/149,017 also distinguishes itself from prior art phase shift techniques by the fact that it does not embed a hidden latent image within an image and therefore also does not reveal such a latent image. The elevation profile is embedded within a base layer sets of lines and reveals, thanks to a corresponding matching revealing layer, the elevation profile's level lines.
Chapter 10 of the book by I. Amidror, The Theory of the Moiré Phenomenon, Kluwer, 2000, entitled “Moiré between repetitive non-periodic layers” describes the theory of the superposition of curvilinear line gratings by relying on Fourier series decomposition and spectral domain analysis. Chapter 11 of the same book gives an overview over the indicial method enabling obtaining the geometric layout of the superposition of curved line gratings. In problems 11.4 and 11.5 of Chapter 11 and in the paper by J. S. Marsh, Contour Plots using a Moiré Technique, American Journal of Physics, Vol. 48, January 1980, 39-40, a moiré technique is described for drawing the contour plot of a function g(x,y) which relies on the superposition of a straight line grating and of a curved line grating whose lines have been laterally shifted by an amount equal to g(x,y). These book chapters, together with problems 11.4, 11.5 and the paper by J. S. Marsh however (a) do not consider generating a shape elevation profile from a preferably bilevel motif shape image, (b) do not mention the possibility of having level lines moving between shape borders and the shape centers and (c) do not consider contour plots as a means of creating pulsing shapes enhancing the attractiveness of valuable articles.
The geometric properties of the moiré produced by the superposition of two rectilinear or curvilinear line gratings are described by K. Patorski, The moiré Fringe Technique, Elsevier 1993, pp. 14-16. Moiré fringes (moiré lines) produced by the superposition of two line gratings (i.e. set of lines) are exploited for example for the authentication of bank notes as disclosed in U.S. Pat. No. 6,273,473, Self-verifying security documents, inventors Taylor et al. Neither Patorski's book, nor U.S. Pat. No. 6,273,473 consider modifying a line grating according to a shape elevation profile nor do they consider generating a shape elevation profile from an initial, preferably bilevel, motif shape image. They also don't mention the possibility of having, by superposing base and revealing layers, level lines moving between motif shape boundaries and motif shape centers.
The well-known parallax effect has been described in U.S. Pat. No. 5,901,484 to R. B. Seder in the context of creating a display device for displaying a plurality of images. Parallax images and the parallax effect is also described in the book by R. L. Van Renesse, Optical Document Security, 2nd ed., 1998, Artech House, section 9.3.1 Parallax Images and section 9.3.2, Embossed Lens Patterns, pp. 207-210, hereinafter referenced as [VanRenesse98]. In section 9.3.2 of that book, FIG. 9.5 shows an example of embossed cylindrical microlenses (also called lenticular lenses), where the lenses have a diameter of 300 μm and are embossed on a visually transparent plastic sheet of about 400 μm thickness. Due to the focusing effect of the lenses, only small strips of the bottom layer are visible while the exact location of these strips depends on the viewing angle.
U.S. Pat. No. 6,494,491, to Zeiter et. al. “Object with an optical effect”, teaches a composed layer formed by two images separated by a gap, where due to the relative phase between the two images, a given overall image is perceived at a certain viewing angle and an altered image at other angles. This invention relies on different darkness levels generated by superposed aligned or respectively non-aligned mutually rotated strokes.
There have been attempts to improve the aesthetic quality of watches by incorporating elements having an aesthetic component possibly combined with a functional component such as the watch hands. According to U.S. Pat. No. 4,653,930 to Marlyse Schmid, “it has long been known to add an attractive or original function to the functions of time indication in a timepiece, such as a watch or clock, by causing the appearance of the timepiece to change in the course of time according to the relative position of the indicator members”. U.S. Pat. No. 3,321,905 to Krebs describes a clock display comprising polarization layers where the rotation of one of the layers performed in synchronization with the clock hands creates a visual effect. U.S. Pat. No. 3,890,777 to Stanish describes disks rotating in synchronization with the hour and minutes hands, comprising radial transparent or colored sections, which at certain time points yield a flash illuminating the hour and minute hands. U.S. Pat. No. 4,653,930 to Marlyse Schmid, teaches a timepiece comprising a stationary decorative face with transparent zones and a rotating display bearing the same decorative design. The decorative design appears in the superposition of the stationary face and the rotating display when the two are exactly superimposed.
In respect to watches and clocks, the present invention also uses the rotating mechanisms present in a watch, such as the mechanisms rotating the second-hand for rotating one of the layers, e.g. the revealing layer, in superposition with the fixed base layer located for example on the face of the watch, thereby generating dynamically evolving superposition images such as evolving band moiré images or shape level line images.